Peter Bancroft
To keep it alive you should refresh it every day, or if you're not going to bake with it put it in the fridge and refresh it once every week or so. To be honest I forget sometimes for a month and I'll take it out and refresh it with some warmer water and after a day or so it comes back to life.
I use a 1:5:5 ratio, so I usually do 20g of starter to 100g of water and 100g of flour. I tend to use a 50/50 mix of strong white and wholemeal, but it depends of your preference.